Method of making spark plugs



27, 1929- F. F. HAMILTON I METHOD OF MAKING SPARK PLUGS Filed Aug. 17, 1928 [/1 Vin Tor 1 77M 1'0 F Hand/fan,

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STATES FRANCIS F. HAMILTON, OF INDIANAPOLIS, INDIANA.

METHOD OF MAKING SPARK PLUGS.

Application filed. August 1'7, 1928.

This invention relates generally to spark plugs of the type commonly employed in automotive internal combustion engines, and more particularly to the process of making a spark plug and its resultant product. The primary object of the invention is to form a spark plug in a manner, that, while extremely durable, can be produced at a cost far under any method or structure heretofore known.

The invention is described in the form new best known to me as shown in the accoi'npanying drawing, in which Fig. l, is a fragmentary side elevation of a blank following the first operation there on;

Fig. 2, a fragmentary side elevation of the blank after being drawn to the tube;

Fig. 3, a side elevation of the tube with a hexagon head formed thereon;

Fig. 4, a top plan view of the form shown in Fig. 3;

Fig. 5, a central longitudinal vertical sec tion through the tube on the line 5.5 in Fig. 3;

Fig. 6, a central longitudinal vertical sec tion through the tube after further shaping;

Fig. 7, a top plan view of the center disc;

Fig. 8, a section through the disc on the line 8-8 in Fig. 7.

Fig. 9, a side elevation of" the finished spark plug shell;

Fig. 10, a longitudinal vertical section through the shell with a porcelain positioned therein, and

Fig. 11, a side elevation of the complete plug.

Like characters of reference indicate like parts throughout the several views.

Referring to the drawing, a flat, circular piece of drawing steel 8, Fig. 1, is taken with an external diameter of approximately three and one-half inches and is put through a press to be cupped as in Fig. 1. The blank is then further drawn into a tube 10, Fig. 2 with the section 9 of reduced diameter at the lower end, which remains closed across the end.

The tube 10 so formed is then placed in a press and by suitable dies, the hexagon head 11. is formed from the section 9, Figs. 3, 4, and 5.

When the head 11 is formed, an internal shoulder 13 is produced within the tubing 10, and a steel. disc 14, Fig. 7, of an outside diameter permitting it to be slipped into Serial No. 300,164.

the tube 10 from} below is pressed against this shoulder 13. The disc is cupped, Figs. 7, and 8, and is placed with the concave side downwardly, as indicated by the dotted lines flattened out, and holes 12 and 19 are drilled through the head 11 and disc 14 respectively.

The resultant product is then machined as in Fig. 9, where threads 17 are cut on the shank 18 below the ring 16 and the underside of the ring is turned to a smooth surface normal to the shank 18.

A spark plug porcelain 20 of the usual construction well known to those versed in the art, having a positioning ring 21 therearound, and a central electrode 22, is inserted upwardl through the hole 19 with an annular gas ct 23 around the porcelain between the underside of the disc 14 and the top of the ring 21, to have the upper end of the porcelain project on out through the top hole 12, Fig. 10.

The porcelain 20 is compressively held against the disc 14 with the gasket 23 therebetween, and metal 24 is forced in through the hole 12 around the porcelain 20 projecting therethr'ough to entirely fill the space above the disc 14, the hole 12 being larger in diameter than the diameter of that part of the porcelain extending through it.

Rings 25 are preferably provided on the porcelain 20 around which the metal 24 may flow and solidify to grip the porcelain against displacement and retain the porcelain tightly seated against the disc 14 after the initial external pressure from below is removed. The metal 24 is preferably of a pewter nature, such as a mixture of antimony, copper, lead, or bismuth with tin, the essential feature of the mixture being that it flow readily to fill completely the cavity in the head about the porcelain and after solidifying have a coefficient of expansion closely approximating that of the porcelain.

An electrode 26 is fixed in the lower end of the shank 18 in the usual manner well known to those versed in the art.

llO

I claim:

1. The method of making a spark plug consisting of forming a head on a length of tubing, forming an annular shoulder in the tubing under the head, pressing a disc against the shoulder, drawing in the tubing below the disc to form a shoulder under and compr ssively against the disc,'passing a porcelain up through the disc to have its upper end extend for a substantial distance through the top of said head, and filling the head with metal to retain the porcelain.

The method of making a spark plug l sting of drawing a fiat blank into a l '3 h of tubing, forming a head on the tubing forming thereby an annular shoulder in the tubing head, pressing a disc against the alioulder, drawing in the tubing below the disc to form a shoulder under and compressively against the disc, passing a porcelain rp through the disc to have its upper end extend for a substantial distance through the top of said head, and filling the head with metal to retain the porcelain, said porcelain having an annular shoulder and pressure being applied to the porcelain to press said shoulder toward said disc while said metal is being placed in the head.

3. The method of making a spark plug consisting of forming a head on the end of a piece of tubing pressing a disc in the tubing against the head, forming a shoulder of the tubing against the disc, inserting a porcelain centrally through the disc and filling the head with metal to grip said porcelain therein. I

t. The method of making a spark plug shell consisting of drawing a flat blank into a tube closed on one end, forming a head on the closed end and a shoulder within the tube, placing a disc against the shoulder, said disc being concave downwardly from the shoulder, reducing the tube below the disc and swedging the disc, drilling holes through the tube end and disc, and threading the outer tube surface.

5. The method of making a spark plug shell consisting of forming a head on the end of a tube, positioning a disc in the tube, and reducing the tube below the disc.

In testimony whereof I afilX my signature,

FRANCIS F. HAMILTON. 

